A surge condition is a violent instability condition (typically following an incipient surge or stall condition) which occurs in turbo compressors such as axial flow and centrifugal compressors. The condition is well known to those versed in the art and its onset depends on both the volumetric flow rate and the pressure ratio to which the compressor is subjected. Different types of turbo compressors have differing surge characteristics, but all are subject to the problem.
The surge condition can be caused by anything which either raises the discharge pressure, lowers the suction pressure, or reduces the gas flow to the compressor. In the art with which we are most familiar, most surging problems are caused by poor maintenance, failure of system components (such as cooling tower fans typically used with centrifugal compressor chiller packages), greatly over-sized units, or simple human errors such as failure to open a valve. When a compressor component fails from prolonged surging, the cause is not always easily determinable. However, in our experience, machines that have a history of repeated failures of bearings and impellers are usually found to have had surge problems. Thus, we believe that the provision of a low cost effective surge protection and control device would significantly reduce warranty cost and improve the reliability of units subject to surge.